This invention relates to a process for producing a resin body having several thicknesses by varying the thickness of the formed body during the extrusion process.
Previously, when a resin formed body having different thicknesses is to be produced by an extrusion process, the thickness is altered by increasing or decreasing the take-up speed of the formed body extruded during the extrusion forming process. In such a process, however, the compression or tension forces acting on the body being extruded vary during the readjustment of dimension or during cooling, resulting in wrinkles or cracks in the formed body. Alternatively, the compression or tension remains as a strain causing an unfavorable effect on the products produced.
Also, in such a process, the take-up speed cannot be varied by more than 50 % without detrimentally affecting the resin body formed. Thus it is difficult to change the thickness by a large amount. Moreover, there is tendency for the transient portions from the thin portion to the thick portion or the reverse thereto to become longer.